function GeoCalc(){
var Surface;
side = eval(document.circonf.side.value);

if(side > 0){

	Surface = FormatNumber((Math.PI / 4) * side);
	
	document.getElementById("surface").innerHTML = "&#928; = 3.141592653589793<br />Circonférence<br />" + Surface + "  cm<br />" + FormatNumber(Surface/10000) + "  m<br />";
}

}